Nanowire battery methods and arrangements

ABSTRACT

A variety of methods and apparatus are implemented in connection with a battery. According to one such arrangement, an apparatus is provided for use in a battery in which ions are moved. The apparatus comprises a substrate and a plurality of growth-rooted nanowires. The growth-rooted nanowires extend from the substrate to interact with the ions.

FIELD OF THE INVENTION

The present invention relates generally to ion battery arrangement andmethods, and more particularly to nanowire-based electrode arrangementsand approaches involving the assembly or manufacture of nanowireelectrode arrangements.

BACKGROUND

The demand for batteries with high energy capacity, low weight and longlifetime has become increasingly important in a variety of fields andindustries, including those relating to portable electronic devices,electric vehicles, and implantable medical devices. For example, theenergy capacity, weight and cycle life characteristics are often usefulfor improving the functionality of a particular device in which thebatteries are used. In portable electronic devices and implantablemedical devices, these and other related aspects are useful to allow forincreases in power (e.g., from additional processing power) and/orreduction in the size of the devices. In electric vehicles, theseaspects are often limiting factors in the speed, power and operationalrange of the electric vehicles.

Various commercial embodiments of batteries function as anelectrochemical cell that stores and converts chemical energy fromchemical oxidation and reduction reactions into a useable electricalform. The chemical reactions occur in the materials composing the twoelectrodes of the battery, such as reduction occurring in the cathodeand oxidation occurring in the anode. These reactions are due in part toa difference in electrochemical potential between the materialscomprising the anode and cathode. In many ion-based batteries, the twomaterials electrodes are separated by an ionic conductor, such as anelectrolyte, that is otherwise electrically insulating. Each electrodematerial is electrically connected to an electronically conducting,preferably metallic, material sometimes called the current collector.The current collectors can then be connected to one another using anexternal circuit that allows for electron transfer therebetween. Toequalize the potential difference, the anode releases ions (e.g., byoxidizing to form the ions) when electrons are allowed to flow throughthe external circuit. The flow of electrons is balanced by the flow ofions through the electrolyte. The ions then react with the chemicallyreactive material of the cathode. The number of ions that a material canaccept is known as the specific capacity of that material. Batteryelectrode materials are often defined in terms of the energy capacityper weight, for example in mAh/g. Much research has been devoted tocreating and developing higher energy density electrode materials forhigher capacity batteries.

A specific type of battery is a Lithium-ion battery, or Li-ion battery.Li-ion batteries transport Li ions between electrodes to effect chargeand discharge states in the battery. One type of electrode uses graphiteas the anode. Graphite anodes have reversible (rechargeable) capacitiesthat are on the order of 372 mAh/g. Graphite anodes function byintercalation of Li ions between the layered-structure. A limitation insome graphitic anodes is that Li is saturated in graphite at the LiC₆stoichiometry. Materials that can allow for larger amounts of Liinsertion, therefore, have been attractive for use as high capacity Libattery anodes.

Some alternatives to graphite anodes utilize storage mechanisms that donot involve the intercalation of Li ions between layered-structurematerials. For example, some transition metal oxides use a conversionmechanism that can provide relatively high energy anodes of 700 mAh/g.Other alternatives include elements, such as Si, Sn, Bi, and Al, whichform alloys with Li through Li insertion. Some of these elements providerelatively large theoretical energy capacities. Often such elementsexhibit a volume change during Li insertion. For example, pure Si has atheoretical capacity of 4200 mAh/g for Li_(4.4)Si, but has been shown toproduce as much as a 400% volume change during Li insertion (alloying).In films and micron-sized particles, such volume changes may cause theSi to pulverize and lose contact with the current collector, resultingin capacity fading and short battery lifetime. Electrodes made of thinamorphous Si may exhibit improvements in capacity stability over manycycles, but such films seldom have enough active material for a viablebattery. Attempts to increase conductivity using conducting carbonadditives have not completely solved such problems, since upondealloying (delithiation), the particles may contract, and thereby, losecontact with the carbon. Si anodes have been prepared with a polymerbinder such as poly(vinylidene fluoride) (PVDF) to attempt to hold theparticles together, but the elasticity properties of PVDF may not besufficient for the large Si volume change and do not completely mitigatethe poor conductivity. This results in a low coulombic efficiency andpoor cyclability. For example, the use of 10 μm sized Si particles mixedwith carbon black and PVDF has been shown to result in a first dischargecapacity of 3260 mAh/g; however, the charge capacity is only 1170 mAh/g,indicating a poor coulombic efficiency of only 35%. After 10 cycles, thecapacity also faded to 94%. Moreover, conductive additives and bindersadd weight to the electrode, lowering the overall gravimetric andvolumetric capacities of the battery.

These and other characteristics have been challenging to the design,manufacture and use of Li-alloy materials in Li-battery anodes. Asolution has been to use nanostructure battery electrode materials.Nanomaterials include nanowires, nanoparticles, and nanotubes, all ofwhich have at least one dimension in the nanometer dimension.Nanomaterials have been of interest for use in Li batteries because theyhave better accommodation of strain, higher interfacial contact areawith the electrolyte, and short path lengths for electron transport.These characteristics may lead to improved cyclability, higher powerrates, and improved capacity. Current efforts, however, leave room forimprovement.

SUMMARY OF THE INVENTION

The present invention is directed to overcoming the above-mentionedchallenges and others related to the types of applications discussedabove and in other applications. These and other aspects of the presentinvention are exemplified in a number of illustrated implementations andapplications, some of which are shown in the figures and characterizedin the claims section that follows.

According to one example embodiment, an apparatus is provided for use ina battery. The apparatus provides high energy capacity through the noveluse of nanowires that alloy with the ions. A specific example of theapparatus employs nanowires constructed from materials other than carbonto alloy with Li⁺ ions during a charge state of the battery and torelease the Li⁺ ions during a discharge state. Careful growth of thenanowires directly from the substrate, which is connected to the currentcollector, can provide an apparatus having nanowires that aresubstantially all directly connected to the substrate and that extendtherefrom.

According to another embodiment, an apparatus is provided for use in abattery in which ions are moved. The apparatus comprises a substrate anda plurality of nanowires, each being growth-rooted from the substrateand each having an outer surface with molecules that interact with theions.

According to another embodiment of the invention, a battery is providedthat has a stable energy capacity. The battery comprises an iontransporter to provide ions; a first current collector on one side ofthe ion transporter; and a second current collector, located on anotherside of the ion transporter. The second current collector includes asubstrate and a plurality of solid nanowires that are growth-rooted fromthe substrate and that interact with the ions to set the stable energycapacity greater than about 2000 mAh/g.

According to another embodiment of the invention, a battery that isrecharged is provided. The battery comprises an ion transporter toprovide ions, a first current collector on one side of the iontransporter and a second current collector that is located on anotherside of the ion transporter and that includes a substrate and aplurality of solid nanowires. The solid nanowires are growth-rooted fromthe substrate and interact with the ions to set a maximum capacitivefading between subsequent energy charges at less than about 25 percent.

According to another embodiment of the invention, a battery is providedthat has an energy capacity. The battery comprises a first currentcollector having a substrate, a second current collector, an iontransporter located between the first and second current collectors, theion transporter providing ions, and a layer of nanowires. The layer ofnanowires has a layer height equal to the length of about one of thenanowires. The layer of nanowires also includes nanowires that extendfrom the substrate toward the ion transporter to combine with ions fromthe ion transporter and that set the energy capacity for the battery.

According to another embodiment of the invention, a battery is provided.The battery comprises a first current collector, a second currentcollector, an ion transporter located between the first and secondcurrent collectors and one of the collectors including a substrate, andsolid nanowires to combine with ions provided by the ion transporter fordefining the nominal energy capacity. A preponderance of the solidnanowires are located on the substrate and have an end located on thesubstrate.

According to another embodiment of the invention, a method of anelectrode arrangement that has a substrate for connecting to a currentcollector is implemented. The electrode arrangement is designed for usein a battery. The method comprises the step of growing solid nanowiresfrom the substrate.

According to another embodiment of the invention, a method isimplemented for assembling an electrode arrangement for use in abattery. The method comprises attaching a substrate with growth-rootedsolid nanowires to a current collector, forming a current collectorassembly with an ion transporter located between the substrate andcurrent collector and another current collector; and placing the currentcollector assembly within a housing.

The above summary is not intended to describe each illustratedembodiment or every implementation of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thedetailed description of various embodiments of the invention thatfollows in connection with the accompanying drawings, in which:

FIG. 1 shows an apparatus for use in a battery in which ions are moved,according to one embodiment of the present invention;

FIG. 2 shows a battery cell having nanowires, according to an embodimentof the present invention;

FIG. 3 shows the functionality of a lithium-ion battery cell havingnanowires on the current collector anode, according to an exampleembodiment of the present invention;

FIGS. 4A, 4B and 4C show various stages in producing a structure for usein an ion-battery, according to an example embodiment of the presentinvention; and

FIGS. 5A, 5B, 5C and 5D show results of an experimental batteryarrangement; according to an example embodiment of the presentinvention.

While the invention is amenable to various modifications and alternativeforms, examples thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments shown and/or described. On the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention.

DETAILED DESCRIPTION

The present invention is believed to be applicable to a variety ofdifferent types of ion batteries and devices and arrangements involvingnanowire electrodes. While the present invention is not necessarily solimited, various aspects of the invention may be appreciated through adiscussion of examples using this context.

Consistent with one embodiment of the present invention, a battery isimplemented with an anode, a cathode, current collectors contacting theanode and cathode, and an electrolyte. The negative electrode or anodeis composed of a plurality of nanowires extending from a substrate. Thenanowires have an outer surface with multiple molecules that interactwith the ions. The substrate from which the nanowires extend is attachedto a current collector. The material comprising the current collectorcan include, but is not limited to, stainless steel, copper, nickel,aluminum, and other preferably metallic materials that are inert to Li.The current collector can also be comprised of a flexible material suchas plastic that is coated with a layer of metal, such as copper ornickel, in order to make it electronically conducting. In a specificembodiment, the nanowires are grown from the substrate in such a mannerso as to produce nanowires with one end of the nanowire in directcontact with the substrate and the other end of the nanowire extendingaway from the substrate.

In connection with another embodiment of the present invention, anarrangement for use in a battery is implemented. The arrangementincludes solid nanowires that are growth rooted from a substrate. Thesubstrate is attached to a current collector. In this fashion, thearrangement can be used as an electrode in the battery.

In connection with another embodiment of the present invention, abattery is implemented with a stable energy capacity. An iontransporter, such as an electrolyte, allows ions to move betweenelectrodes located on either side of the ion transporter. One of theelectrodes has a substrate. A plurality of nanowires is growth-rootedfrom the substrate. These nanowires interact with the ions to set thestable energy capacity greater than about 2000 mAh/g. Thus, the batterymaintains the energy capacity through several charge and dischargecycles. These nanowires are non-fullerene type nanowires that allow forthe diffusion of the ions into the nanowire.

In connection with another embodiment of the present invention, abattery is implemented with using nanowires extending from a substrate,where the nanowires provide a stable energy capacity that can be lessthan 2000 mAh/g.

In a specific instance, the diffusion of ions into the nanowire resultsin the nanowire temporarily being composed of an alloy of the diffusedions and the underlying nanowire material. A specific example of such analloy is Li_(4.4)Si formed from the diffusion of Li ions into Sinanowires. Other examples of potential nanowire materials include Ge andSn as well as various metal oxides, nitrides, and phosphides, such asSnO₂, TiO₂, Co₃O₄, Li_(2.6)Co_(0.4)N, Li₃N, LiMnN, FeP₂, CuP, CoP₃ andMnP₄. Additionally, the nanowires may be constructed to contain an alloyof these materials with another material, for example a Si—Ge alloy or aSi—Sn alloy.

Consistent with another embodiment of the present invention, a method ofproducing a battery arrangement is implemented. Nanowires are growndirectly on a current collector substrate thereby making directelectronic contact between the nanowires and the current collector. Afew methods by which this can be done include using vapor-liquid-solid(VLS) or vapor-solid (VS) growth methods.

In a specific example, Si nanowires are synthesized using SiH₄decomposition. The substrate for the growth may be a suitable conductor,such as a metallic material, or more particularly, a stainless steel 304foil. Catalysts, such as gold, are deposited on the current collectorsubstrate provided either from colloid solution or by depositing a thinfilm of Au using e-beam evaporation or sputtering. Alternatively,nanowires can be grown on a substrate using template-free solution phasemethods, including but not limited to solution-liquid-solid (SLS)growth, solvothermal, hydrothermal, sol-gel, and supercriticalfluid-liquid-solid (SFLS).

The resulting nanowires may exhibit diameters that range in size andthat are specifically tailored to an application. Careful selection ofthe diameter can be accomplished by balancing a number of factors. Forexample, nanowires having suitable small diameters may be lesssusceptible to dissociation from the substrate due to ion-insertion (ordeinsertion) strain. Such strain may result in dissociation of thenanowires from the current collector (e.g., due to pulverization of thematerial), resulting in a reduction of the energy capacity. Largerdiameters may increase the total volume of nanowire material on thesubstrate; however, larger diameters may result in the ions not fullydiffusing into the center of the nanowire. Such failure to fully diffusemay result in a corresponding decrease in the energy capacity per gramof the nanowires because a portion of the nanowire has not been used.These and other factors may be used to determine the optimal nanowiresize.

Some of the various nanowire arrangements and methods discussed hereinmay be particularly useful for providing nanowires that aresubstantially all directly connected with the metallic currentcollector. Such connected nanowires contribute directly to the capacitywithout the use of intervening conductive material. These connectednanowires may also be constructed so as to withstand volumetric changesexhibited during the cycling of the battery. Thus, some arrangements andgrowth methods may be useful for avoiding the use of binders orconducting additives, which can add extra weight and lower the overallcapacity of the battery. Moreover, some nanowires allow for direct (1dimensional) electron pathways along the length of the wire to thecurrent collector. This may be particularly useful for efficient chargetransport to the current collector. In one instance, this electrode isused as the anode, or negative electrode, of the battery

In a particular embodiment of the present invention, the positiveelectrode, or cathode, may contain an electrode that is similar to theanode in that it has a plurality of nanowires extending from a currentcollector substrate. These nanowires can be grown using the vapor phaseand template-free solution phase methods previously mentioned.Alternatively, the cathode may be composed of powder composite materialsthat are presently used in a Li-ion battery. While the present inventionis not limited to such examples, a few examples of commerciallyavailable cathode materials are LiCoO₂, LiFePO₄, LiMnO₂, LiMn₂O₄, andLiNiO₂. Between the two electrodes is an ionically conducting,electronically insulating region that includes an electrolytefacilitating transport of ions between the electrodes. This regionincludes a membrane separator soaked with electrolyte, the electrolytebeing a Li salt dissolved in an organic solvent, for example, 1 M LiPF₆in 1:1 w/w ethylene carbonate:diethyl carbonate. Alternatively, theelectrolyte can be a Li salt mixed with a solid ionically conductingmaterial such as a polymer or inorganic material.

According to various example embodiments of the present invention, ananowire apparatus provides a stable energy capacity greater than about2000 mAh/g. In a particular instance, the nanowires grown from thesubstrate initially exhibit a crystalline structure. After a firstcharge and a first discharge cycle, a portion (or all) of the nanowirescan be transformed into an amorphous state. This is believed to be dueto the insertion of the ions into the molecular structure of thenanowires, thereby disrupting the crystalline structure of thenanowires. A charge cycle may also result in an increase in the size ofthe nanowires. For instance, crystalline structures formed from Si havebeen shown to exhibit a 400% increase in size after the formation of aSi—Li alloy. The growth of sufficiently small nanowires may beparticularly useful for adequate strain relaxation and betteraccommodation of large volume changes without fracturing. The nanowirescan also be grown so as to have relatively short ion (e.g., Li)diffusion pathways. In some instances, a 1-dimensional electron pathwayis exploited by growing the nanowires directly on the current collectorsubstrate, thereby electrically addressing each nanowire and allowingfor continuous electron transport pathways down the length of eachnanowire.

Turning now to the figures, FIG. 1 shows an apparatus for use in abattery in which ions are moved, according to one embodiment of thepresent invention. Nanowires 104 extend from substrate 102 and areadapted to interact with ions 106 during charging and discharging of thebattery.

In one instance, nanowires 104 are non-fullerene nanowires growth rootedfrom substrate 102. Rather than using intercalation into a layeredmaterial, such as single-walled nanotubes (SWNT) and multi-wallednanotubes (MWNT) made from carbon, the non-fullerene nanowires use analloying mechanism to interact with the ions. This can be particularlyuseful for providing a high-energy-capacity battery.

The nanowires 104 can be constructed from various materials thatinteract appropriately with the ions 106 (e.g., store ions during chargeand release ions during discharge).

FIG. 2 shows a battery cell having nanowires, according to an embodimentof the present invention. Battery 200 is connected to load/chargecircuit 204. When operating in discharge mode, battery 200 providescurrent to circuit 204. When operating in charge mode, current fromcircuit 204 is used to charge battery 200. Current collectors 206 and212 are conductors that make electronic contact to the anode andcathode. In a specific embodiment the current collectors are metal andunreactive to Li.

Nanowires 202 are connected to the current collector 212. In a specificembodiment, current collector 212 is part of the anode of battery 200.The nanowires interact with ions from ion source 208. Ion source 208 mayinclude a material that contains Lithium, such as LiCoO₂. Separator 210may be optionally implemented to maintain physical separation betweenthe ion source 208 and the nanowires 202 while allowing ions from ionsource 208 to pass. This may be accomplished by the use of variousporous materials. In another instance, ion source 208 can include asolid source of ions, such as a Li foil. In yet another instance, ionsource 208 can include nanowires composed of a cathode materialconnected to current collector 206.

According to one embodiment of the present invention, the currentcollectors are arranged as parallel sheets separated by the ion source.

In other embodiments the current collectors can be arranged in variousorientations. For instance, the current collectors may be arranged in aconcentric, cylindrical fashion. This can be particularly useful forcreating batteries that have a similar form factor to current batterytechnologies, such as C, AA, AAA cell-sized batteries. In anotherinstance, a plurality of battery cells, each having respective anode,cathode and ion sources, may be arranged in series and/or parallelconfiguration to form a single battery with the desired capacity andvoltage characteristics.

FIG. 3 shows the functionality of a lithium-ion battery cell havingnanowires on the current collector anode, according to an exampleembodiment of the present invention. Current collectors 304 and 308provide an interface from the load 310 to both the anodal nanowires 302and the cathode portions 306. In a particular embodiment, cathodeportions 306 can be constructed from nanostructures; the invention,however, is not limited to such an embodiment. The anodal nanowires 302receive and accept with Li⁺ ions during a charge state, for example byalloying. Such a charge state is implemented by application of anappropriate voltage to current collectors 304 and 308. Energy from theapplied voltage is stored, for example, in the form of a nanowire-Lialloy. Cathode portions 306 release Li⁺ ions during the charge state. Ina specific example, the cathode is a metal oxide (e.g., LiCoO₂) thatchanges its oxidation charge during the charge state. For instance, inthe case of LiCoO₂, the charge state is a higher oxidation state thanthe discharge state, where Co³⁺ oxidizes to Co⁴⁺ releasing a Li⁺ ion tothe electrolyte. Thus, more ions are free to react with the anodalnanowires during the charge state.

As shown in FIG. 3, the Li+ ions can be part of an electrolyte that islocated in the area between the anode and cathode. This allows the Li+ions freedom to move between the anode and cathode during either of thecharge and discharge states. In one instance, a porous separator layeris used to provide structural support between the anode and cathode,while still allowing for the movement of Li+ ions therebetween. Specificembodiments of the present invention implement battery using anelectrolyte that has Li salt dissolved in an organic solvent. A specificexample is 1.0 M LiPF₆ in 1:1 w/w ethylene carbonate:diethyl carbonate.The electrolyte can also be a Li salt dissolved with a polymer orinorganic material.

The structure of FIG. 3 can be assembled by forming an electrodearrangement that has an ion transporter located between the currentcollectors of the anode and cathode. One of the anode and cathodeincludes a substrate that has solid nanowires grown therefrom. Thisstructure can then be surrounded by a suitable housing, such as aninsulating material with at least two conductive terminals. One terminalis used to electrically connect to the anode portion of the structure,while another terminal is electrically connected to the cathode portionof the structure. In a specific embodiment, the structure can be shapedto conform to form factors of commercially available batteries.

FIGS. 4A-4C show various stages in producing a structure for use as ananowire electrode in an ion-battery by using a vapor-liquid-solidgrowth (VLS), according to an example embodiment of the presentinvention. In FIG. 4A, catalysts 404 are deposited directly ontosubstrate 402. Substrate 402 is made from a suitable conductor, such asa metallic material, or more particularly, a stainless steel foil. Otherexamples of suitable conductors include copper, nickel, aluminum, or aflexible material such as plastic coated with a metal. Catalysts 404,such as gold, are provided either from colloid solution or by depositinga thin film of Au using e-beam evaporation or sputtering. Other suitablecatalysts are determined by the particular nanowire material system ofinterest. Alternatively, no catalyst may be needed when using atemplate-free solution phase method to grow nanowires directly on thecurrent collector surface.

FIG. 4B shows the growth of nanowires 406 on the substrate 402.Vapor-liquid-solid (VLS) or vapor-solid (VS) growth methods are thenused to produce nanowires that are connected to the substrate and thatextend therefrom. Examples of such techniques are described in moredetail in A. M. Morales, and C. M. Lieber, Science 279, 208 (1998); M.H. Huang, et al. Adv. Mater. 13, 113-116 (2001); Dick, K. A. et al. Adv.Funct. Mater. 15, 1603-1610 (2005); Pan, Z. W., et. al. Science 291,1947-1949 (2001), each of which are fully incorporated herein byreference. In a specific example, Si nanowires are synthesized usingSiH₄ decomposition.

FIG. 4C shows the completion of the growth of nanowires 406 fromsubstrate 402. In a specific embodiment the nanowires are on the orderof tens of microns in length and between 50 nm and 300 nm in diameterprior to a charge-discharge stage. Due to the process of growth, amajority of the nanowires may exhibit a substantially vertical growthfrom substrate. This may be characterized in a specific example wherethe majority of the nanowires have an angle greater than about 50degrees from the substrate as shown by angle X.

According to a specific embodiment of the invention, Si nanowires(SiNWs) are grown from the substrate using an Au catalyst.Single-crystalline SiNWs are grown inside a tube furnace using thevapor-liquid-solid growth method. Stainless steel 304 (0.002″ thick)foil substrates are decorated with Au catalysts, either byfunctionalizing with 0.1% w/v aqueous poly-L-lysine solution and dippinginto 50 nm diameter Au colloid solution, or by evaporating 75 nm Auusing e-beam evaporation and annealing for 30 min at 530° C. just priorto growth. The substrates were heated to 530° C. and silane (SiH₄, 2% inAr) was flowed in at 80 sccm with a total chamber pressure of 30 Torr.

In this example, the electrochemical properties of the SiNW electrodewere evaluated using cyclic voltammetry. The charging current associatedwith the formation of the lithium-silicide compounds Li₁₂Si₇ starts at˜330 mV and shows a peak at 25 mV, corresponding to the formation ofLi₂₁Si₅. The charging peaks at 370 and 620 mV represent thedelithiation, which is consistent with previous studies done onmicrostructured silicon anodes. These characteristic current peaksincrease with cycling because the scan rate is fast and more SiNWs areactivated with cycling. The Au catalyst was also electrochemicallyactive, with lithiation beginning at ˜150 mV. The delithiation peak wasvisible at ˜180 mV in the SiNW sample. Both cyclic voltammetry andconstant current measurements on a control sample with a 75 nm Au filmon stainless steel showed that the current associated with Au alloyingand dealloying with Li are low compared to that for the SiNWs, with aninitial discharge capacity of 20 mAh/g that decayed to <10 mAh/g after10 cycles. Thus, the capacity contribution from Au may be considerednegligible in the SiNW electrodes. In other embodiments the catalyst maybe removed to avoid any such contribution.

FIGS. 5A-5D show results obtained from an experimental implementation ahalf-cell that was constructed with a plurality of Si nanowires (SiNWs)grown on a stainless steel substrate as one electrode and lithium foilas the other electrode, according to one example embodiment of thepresent invention. The electro-chemical properties were performed in aglass cell with 1.0 M LiPF6 electrolyte in 1:1 w/w ethylenecarbonate:diethyl carbonate as solvent. Li insertion into the SiNWs wasfound to exhibit a relatively high energy capacity.

FIG. 5A shows a cyclic voltammogram measured over the range from 2.0 to0.01 V vs. Li/Li⁺ with a scan rate of 1 mV/s. The charge currentassociated with the formation of the Li—Si alloy started at ˜330 mV andbecame quite large below 100 mV. Upon discharge, current peaks appearedat about 370 and 620 mV. FIG. 5B shows results of the first and secondcycles at the C/20 rate. The voltage profile observed was consistentwith previous studies on Si anodes, with a long flat plateau during thefirst charge, during which amorphous LixSi is being formed fromcrystalline Si. Subsequent discharge and charge cycles have differentvoltage profiles, characteristic of amorphous silicon. The observedcapacity during this first charging operation was 4277 mAh/g, which isessentially equivalent (i.e., within experimental error) to thetheoretical capacity. The first discharge capacity was 3124 mAh/g,indicating a coulombic efficiency of 73%. The second charge capacitydecreased by 17% to 3541 mAh/g although the second discharge capacityincreased slightly to 3193 mAh/g, giving a coulombic efficiency of 90%.FIG. 5D shows that both charge and discharge capacities remained nearlyconstant for subsequent cycles with little fading up to 10 cycles. FIG.5D also shows charge and discharge data along with the theoreticalcapacity (372 mAh/g) for lithiated graphite currently used in lithiumbattery anodes, and the charge data for thin films containing 12 nm Sinanocrystals (NCs). The SiNWs displayed high capacities at highercurrents as well. FIG. 5C shows the charge and discharge curves observedat C/10, C/5, C/2, and 1 C rates. Even at the 1 C rate, the capacitiesremained >2100 mAh/g.

While the present invention has been described above and in the claimsthat follow, those skilled in the art will recognize that many changesmay be made thereto without departing from the spirit and scope of thepresent invention. Such changes may include, for example, the use of anumber of different alloy combinations for the nanowires. In addition,the batteries may be constructed using a plurality of cells, eachcontaining a current collector with nanowires for interacting with theions. These and other approaches as described in the contemplated claimsbelow characterize aspects of the present invention.

1. A battery, comprising: an ion transporter to transport ions; a firstcurrent collector on one side of the ion transporter; and a secondcurrent collector, located on another side of the ion transporter,including a substrate and a plurality of solid nanowires includingsilicon or a silicon alloy that are growth-rooted from the substrate andthat interact with the ions, wherein the growth-rooted solid nanowireshave a stable energy capacity greater than about 2000 mAh/g.
 2. Theapparatus of claim 1, wherein the nanowires have an average outerdiameter that is greater than 50 nanometers, and wherein the stableenergy capacity is stable over at least ten discharge and charge cycles.3. The battery of claim 1, wherein the nanowires have an average outerdiameter that is less than 300 nanometers.
 4. The battery of claim 1,wherein the nanowires have an average outer diameter in a range from 50to 300 nanometers, and wherein the stable energy capacity is stable overat least ten discharge and charge cycles.
 5. A battery, comprising: anion transporter to transport ions; a substrate; a first currentcollector on one side of the ion transporter; and a second currentcollector, located on another side of the ion transporter, including thesubstrate and a plurality of solid nanowires including silicon or asilicon alloy that are growth-rooted from the substrate and thatinteract with the ions, wherein the growth-rooted solid nanowires have astable energy capacity greater than about 2000 mAh/g over at least tendischarge and charge cycles, and each of the plurality of nanowireshaving an outer surface with molecules that interact with the ions. 6.The battery of claim 1, wherein the plurality of solid nanowires thatare growth-rooted from the substrate are configured to interact with theions to set a maximum capacitive fading between subsequent batterycycling at less than about 25 percent.
 7. The battery of claim 1,wherein, in a discharge state, the solid nanowires are Si.
 8. Thebattery of claim 1, wherein, in a discharge state, the silicon alloycomprises one of Ge and Sn and of another material.
 9. The battery ofclaim 1, wherein, in a charge state, the solid nanowires have amorphousportions that include an alloy formed from the combination of the solidnanowires and the ions.
 10. The battery of claim 1, wherein thenanowires are directly connected to the substrate.
 11. The battery ofclaim 1, wherein a majority of the nanowires have an angle greater thanabout 60 degrees from the end located on the substrate and a second end,the angle being such that 90 degrees is perpendicular to a surface ofthe substrate at which the first end is located.
 12. A battery,comprising: an ion transporter to transport ions; a substrate; a firstcurrent collector on one side of the ion transporter; and a secondcurrent collector, located on another side of the ion transporter,including the substrate and a plurality of solid nanowires includingsilicon or a silicon alloy that are growth-rooted from the substrate andthat interact with the ions, wherein the growth-rooted solid nanowireshave a stable energy capacity greater than about 2000 mAh/g over atleast ten discharge and charge cycles, and each of the plurality ofnanowires having an outer surface with molecules that interact with theions, wherein each of a majority of the nanowires have an angle greaterthan about 60 degrees from an end of the nanowire located on andconnected to the substrate and a second end of the nanowire, the anglebeing such that 90 degrees is perpendicular to a surface of thesubstrate at which the first end is located.
 13. The battery of claim12, wherein, in a discharge state, the solid nanowires include an alloyof Si.
 14. The battery of claim 12, wherein substantially all of thenanowires are directly connected to the substrate.
 15. The battery ofclaim 1, wherein the ion transporter is electrolyte.
 16. The battery ofclaim 15, wherein the electrolyte comprises a lithium salt dissolved inan organic solvent.
 17. The battery of claim 16, wherein the lithiumsalt is LiPF6.
 18. The battery of claim 16, wherein the organic solventcomprises one or more solvents selected from the group consisting ofethylene carbonate and diethyl carbonate.
 19. The battery of claim 15,wherein the electrolyte is configured to transport ions along the lengthof the plurality of solid nanowires.
 20. The battery of claim 19,wherein the plurality of solid nanowires are configured for facilitatingdiffusion from the electrolyte that contacts side walls of the pluralityof solid nanowires to centers of the plurality of solid nanowires. 21.The battery of claim 15, further comprising a porous separator layersoaked with the electrolyte.
 22. The battery of claim 21, wherein theporous separator layer is configured to maintain physical separationbetween the first current collector and the second current collector andconfigured to allow the ions to pass through the porous separator layer.23. The battery of claim 1, wherein the first current collector is apositive electrode.
 24. The battery of claim 1, wherein the secondcurrent collector is a negative electrode.
 25. The battery of claim 1,wherein the substrate comprises metallic material.
 26. The battery ofclaim 1, wherein the substrate comprises one or more materials selectedfrom the group consisting of stainless steel, copper, nickel, andaluminum.
 27. The battery of claim 1, wherein the substrate comprises astainless steel foil.
 28. The battery of claim 1, wherein the pluralityof solid nanowires comprises a non-fullerene material selected from thegroup consisting of silicon, germanium, tin, and combinations thereof.29. The battery of claim 1, wherein the plurality of solid nanowires areconfigured to substantially withstand volumetric changes exhibitedduring cycling of the battery without fracturing.
 30. The battery ofclaim 1, wherein the first current collector and the second currentcollector are wound in a cylindrical concentric fashion.
 31. The batteryof claim 1, wherein the stable energy capacity corresponds to a cyclingrate of at least about 1 C.
 32. The battery of claim 1, wherein thesolid nanowires include at least some catalyst.
 33. The battery of claim1, wherein the ion transporter comprises a liquid electrolyte, andwherein the stable energy capacity of the solid nanowires is set atleast in part by the presence of a non-fullerene material comprisingsilicon in the nanowires and growth-rooting of the nanowires to ametallic substrate, and wherein the plurality of growth-rooted solidnanowires resist fracturing during volumetric changes exhibited duringbattery cycling.